The present invention pertains generally to cryogenics and more particularly to composite superconductors.
In superconductor magnets, variations in magnetic fields are a common occurrence which often cause conduction faults in the superconducting filaments. For this reason, these filaments are normally surrounded by a stabilizing metal such as copper or aluminum which is conductive across a wide range of temperatures, including superconducting temperatures. Flux jumps, wire motion, or eddy currents of the copper, produce heat which oftentimes drives the temperature of the superconducting filaments beyond the temperature range for superconducting operation, at which point, these filaments become almost totally nonconductive. The local loss of superconductivity due to such a fault normally produces additional heat from resistance losses or other causes, which, in turn, creates further temperature excursions, thereby creating a runaway undampened temperature excursion cycle. Since the heat transfer process occurs very rapidly in the conductor, i.e., on the order of a few microseconds, the cryogenic fluid is incapable of absorbing the locally produced heat. This is a result of the fact that the heat transfer process between the surface of the superconductor and the helium is slow due to the poor heat conduction attributes of the helium. The cycle can therefore proceed in an undampened mode to produce major interruptions in electron flow. Moreover, the low specific heat of the copper renders this material incapable of absorbing temperature excursions of the superconducting filaments thereby further aiding this undampened runaway temperature excursion cycle.